Bowel (colorectal) cancer in young adults is still uncommon, but in many countries, including the USA and England, it has become more common in people under 50 [1, 3]. The full cause is not yet clear; family history, obesity, heavy drinking and changes in gut bacteria are among the factors being studied [4, 5, 6]. The most common symptoms in young people are blood in the stool, tummy pain and a change in bowel habit, and anaemia is another sign [7]; do not ignore these symptoms because you are young, and see a doctor if they continue or come back [11].
Key points
- In a study of 50 countries, bowel cancer in people aged 25 to 49 was rising in 27 of them; in most of these countries the rise was seen only in young adults or was faster in them than in older people [1].
- In the USA, bowel cancer is now the leading cause of cancer death in people under 50 [3].
- Even so, bowel cancer in young adults is still uncommon: even in the countries with the highest rates, about 1 in every 6,000 adults aged 25 to 49 is diagnosed each year [1].
- The most common symptom is blood in the stool: nearly half of young people with bowel cancer first went to the doctor with this symptom, and diagnosis was often delayed by several months [7].
- About 1 in 5 young people with bowel cancer carries an inherited gene change [8]; if bowel cancer runs in your family, you may need a colonoscopy before the age of 45 [10].
Is bowel cancer becoming more common in young adults?
Yes. In a large study of cancer registries in 50 countries, bowel cancer in people aged 25 to 49 had become more common over the previous 10 years in 27 countries; the largest rises were in New Zealand, Chile, Puerto Rico and England [1]. In 20 of these 27 countries, the rise was either seen only in young adults or was faster in them than in older people [1].
In the USA, bowel cancer in adults aged 20 to 49 has become a little more common each year, and deaths from it in people under 50 have also crept up since 2004; over the same period it has become less common in people aged 65 and over [3]. Most of these new cancers are in the last part of the colon and the rectum [3].
This rise means symptoms should be taken seriously at any age, not that every young person is at high risk: bowel cancer in your 20s and 30s is still uncommon, and even in the countries with the highest rates, about 1 in every 6,000 adults aged 25 to 49 is diagnosed each year [1].
What causes colon cancer in young adults?
Researchers do not yet know the full cause of this rise [1, 6]. Studies have linked several factors with a higher risk; most of these are associations, and it has not been proven that they are the main cause of the rise:
- Family history: people whose father, mother, sister, brother or child has had bowel cancer are about 4 times more likely to develop it before the age of 50 [4].
- Obesity: in a study of more than 85,000 female nurses in the USA, women with obesity were almost twice as likely as women of a healthy weight to develop bowel cancer before 50; the more weight they had gained since the age of 18, the higher the risk [5].
- Heavy drinking and high blood fats (cholesterol) were also linked with a higher risk. Studies on diet, inactivity and blood pressure are still few [4].
- Gut bacteria: some gut bacteria make a substance called colibactin that damages the DNA of cells. In a study of nearly 1,000 bowel cancer samples from 11 countries, the traces of this damage were more than 3 times more common in people diagnosed before 40 than in those over 70. The researchers think that exposure to these bacteria in childhood may play a part in the rise [6].
Read more: does obesity cause cancer?, does alcohol cause cancer? and do red and processed meat cause cancer?
Why is cancer increasing in young adults?
According to global estimates, the number of cancers diagnosed before the age of 50 in 2019 was more than one and a half times the number in 1990, and the number of deaths also rose [2]. These figures count patients; they do not take into account that the world's population also grew over this time [2]. Breast, lung, stomach and bowel cancers caused the most deaths at these ages [2].
The same study named an unhealthy diet (a lot of red meat, little fruit, a lot of salt and little milk), alcohol and tobacco as the most important changeable risk factors for early-onset cancers, and recommended a healthy lifestyle to reduce them [2]. Read more: what causes cancer? and can cancer be prevented?
Colon cancer symptoms in young adults: the first signs
In a review of 81 studies of young people under 50 with bowel cancer, the most common symptoms were [7]:
- blood in the stool or bleeding from the back passage: nearly half of patients
- tummy pain: about 4 in 10
- a change in bowel habit (diarrhoea, constipation or both): about 1 in 4
- anaemia, which shows up on a blood test
Blood in the stool was the strongest sign and made bowel cancer at least 5 times more likely [7]. For someone under 50 who has bleeding from the back passage with tummy pain or unexplained weight loss, the UK national guideline recommends a stool test (FIT) to help decide on a colonoscopy; it recommends the same at any age for a change in bowel habit or iron-deficiency anaemia [11]. Read more: symptoms of bowel cancer and what does blood in the stool mean? Piles or bowel cancer.
Why is diagnosis delayed in young people?
Warning signs in young people are often missed or not taken seriously, and this delays the diagnosis [7]. In the same review, it took about 6 months on average from the first symptom to the diagnosis [7].
Bleeding from the back passage also has simpler causes, such as piles (haemorrhoids); but if the bleeding continues, comes back, or comes with tummy pain, a change in bowel habit or tiredness, go back to the doctor and ask whether you need a colonoscopy. If a stool test was negative but the symptoms continue, the UK guideline says further investigation should not be delayed [11].
Who needs screening before 45?
For people at average risk, bowel screening starts at 45 [9]. These groups are screened earlier or differently:
- Family history: if your father, mother, sister, brother or child had bowel cancer or an advanced polyp before the age of 60, or two of them were diagnosed at any age, a colonoscopy every 5 years is recommended from the age of 40, or from 10 years before the age of the youngest relative at diagnosis (whichever is earlier). If one of them was diagnosed at 60 or older, screening starts at 40 [10].
- Inherited conditions such as Lynch syndrome or familial polyposis, and inflammatory bowel disease: these have their own programme [9]. In Lynch syndrome, a colonoscopy every 1 to 2 years has lowered the number of bowel cancers and deaths from it [12].
About 1 in 5 young people who develop bowel cancer carry an inherited gene change, and nearly half of them had no parent, sibling or child with bowel cancer [8]. This is why the researchers suggest that genetic testing be considered for all young people with bowel cancer [8]. Read more: at what age is a screening colonoscopy needed? and is cancer hereditary?
When should I contact a doctor?
Being young is no reason to ignore these symptoms. In the following cases do not wait; see a doctor within the next few days:
- blood in the stool or bleeding from the back passage that keeps coming back, or comes with tummy pain or unexplained weight loss [7, 11]
- diarrhoea, constipation or another change in bowel habit that has lasted several weeks [11]
- iron-deficiency anaemia with no clear cause [11]
- tummy pain that does not go away [7]
- if your stool test was negative but the symptoms continue [11]
If a close relative has had bowel cancer, talk to a doctor about when to have a colonoscopy, even if you have no symptoms [10].
Heavy bleeding from the back passage, or severe tummy pain with vomiting and being unable to pass wind or stool need urgent care; call your local emergency number.
Frequently asked questions
How likely is bowel cancer in young adults?
I am under 30 and have seen blood in my stool; could it be bowel cancer?
Bowel cancer is uncommon at this age [1], but blood in the stool is the strongest sign of bowel cancer in young people [7]; so show it to a doctor. If the bleeding keeps coming back or comes with tummy pain, a change in bowel habit or weight loss, the doctor will usually suggest a stool test or a colonoscopy [11].
Should young people have screening colonoscopies?
For people without symptoms who are at average risk, screening starts at 45 [9]. If you have a family history of bowel cancer, an inherited condition such as Lynch syndrome, or inflammatory bowel disease, you may need it earlier [9, 10]. If you have symptoms, a colonoscopy is no longer "screening"; it is needed to find the cause.
My father was diagnosed with bowel cancer at 45; when should I start having colonoscopies?
For someone whose father, mother, sister, brother or child was diagnosed before 60, the US Multi-Society Task Force recommends a colonoscopy every 5 years from the age of 40, or from 10 years before the relative's age at diagnosis (whichever is earlier) [10]. In this example, that means from the age of 35. If your father has not had genetic testing, also ask about genetic counselling [8].
My stool test was negative but I still have symptoms; what should I do?
Go back to the doctor. The UK national guideline says that if unexplained symptoms continue and the doctor is concerned, referral for further tests should not be delayed because the stool test was negative [11].
What can I do to lower my risk of bowel cancer?
Keeping a healthy weight, cutting down on or avoiding alcohol, and a healthy diet with less red meat and more fruit are linked with a lower risk of early-onset cancers [2, 4, 5]. If you have a family history, timely screening matters most, because polyps can be removed during a colonoscopy before they turn into cancer [10]. Read more: can cancer be prevented? and what are bowel polyps?
Are bowel cancer symptoms different in women and men?
No; the UK national guideline lists the same symptoms for women and men [11]. See: signs of cancer in women and signs of cancer in men.
Early-onset colorectal cancer: epidemiology, risk factors and assessment (for doctors)
For physicians
Incidence trends. In CI5plus data from 50 countries (up to 2017), the incidence of colorectal cancer at 25 to 49 years had increased in 27 countries; the largest AAPCs were in New Zealand (3.97%), Chile (3.96%), Puerto Rico (3.81%) and England (3.59%); in 20 of the 27 countries the rise was either exclusive to the younger group or faster than at 50 to 74 years. The highest early-onset ASR was in Australia (16.5 per 100,000 person-years) and the lowest in India (3.5) [1]. In the USA (2026 report), incidence at 20 to 49 years rose by 3% a year during 2013 to 2022, mainly in the distal colon and rectum, and mortality under 50 has risen by 1% a year since 2004; CRC is now the leading cause of cancer death under 50 [3]. In GBD 2019, the number of early-onset cancer cases (14 to 49 years, all types) rose by 79.1% and deaths by 27.7% between 1990 and 2019 [2].
Risk factors. Meta-analysis of 20 studies: CRC in a first-degree relative RR 4.21 (95% CI 2.61 to 6.79), hyperlipidaemia 1.62, obesity 1.54 and high alcohol consumption 1.71; smoking 1.35 (not significant); heterogeneity was considerable (I² above 60%) except for alcohol [4]. In the Nurses' Health Study II (85,256 women, 114 cases), BMI 30 or above vs 18.5 to 22.9: RR 1.93 (1.15 to 3.25); per 5 BMI units 1.20; weight gain of 40 kg or more since the age of 18: 2.15 [5]. In 981 CRC genomes from 11 countries, the colibactin mutational signatures (SBS88 and ID18) were 3.3 times more common in people diagnosed before 40 than above 70, were imprinted early in tumour development, and ID18 accounted for about 25% of APC driver indels in colibactin-positive cases [6].
Presentation and diagnostic delay. Meta-analysis of 81 studies: haematochezia 45%, abdominal pain 40% and altered bowel habit 27%; haematochezia (estimates 5.2 to 54.0), abdominal pain (1.3 to 6.0) and anaemia (2.1 to 10.8) were associated with a higher likelihood of early-onset CRC; the interval from symptom to diagnosis was a mean of 6.4 months (23 studies) and a median of 4 months (16 studies) [7]. NICE NG12: quantitative FIT under 50 with rectal bleeding plus unexplained abdominal pain or weight loss, and at any age with a change in bowel habit, iron-deficiency anaemia or an abdominal mass; refer with FIT ≥10 micrograms of haemoglobin per gram of faeces; with a negative FIT and strong clinical concern, do not delay referral; a rectal mass or an unexplained anal mass or ulceration can be referred without FIT (1.3.1 to 1.3.3) [11].
Genetics and screening. In 430 patients under 50, about 1 in 5 carried a germline mutation associated with cancer (mostly Lynch: MSH2, MLH1, MSH6, PMS2; then FAP and MUTYH), and only 51% of carriers had CRC in a first-degree relative; multigene panel testing should be considered for all young patients [8]. The USPSTF recommends screening from 45 (grade B for 45 to 49 years); the recommendation does not cover known hereditary syndromes (such as Lynch and FAP), IBD or a personal history of CRC or adenomas [9]. USMSTF 2017: one FDR with CRC or an advanced adenoma before 60, or two FDRs at any age: colonoscopy every 5 years from 40 or from 10 years before the youngest relative's age at diagnosis; one FDR at 60 or older: average-risk options from 40 [10]. In Lynch syndrome, colonoscopy every 1 to 2 years has reduced CRC incidence and mortality [12].
Scientific evidence
Scientific evidence
2 itemsScreening for Colorectal Cancer
Colorectal Cancer Screening: Recommendations for Physicians and Patients From the U.S. Multi-Society Task Force on Colorectal Cancer
Related cancer types
Related questions
References
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Numbers in the text, such as [1], refer to these sources. Sources with a “Study card” button are summarised in the site’s evidence library.
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